Race against time in Liberian Army Worms plague

A team of international experts led by FAO is racing against time to contain a vast plague of voracious Armyworm caterpillars which has triggered a national emergency in Liberia and
could spread to much of West Africa unless resolved soon.

FAO Permanent Representative in Liberia Winfred Hammond said that some 100 villages in northern and central Liberia were now affected and that six communities in neighbouring Guinea had
also been struck. The millions-strong caterpillar hordes devour all vegetation in their path and pollute wells and streams with their excrements wherever they go.

In some cases they overrun homes and buildings, sending inhabitants fleeing in panic. According to Liberian authorities, the emergency involves about 500 000 villagers.

It was not immediately clear whether the plague was rapidly spreading – first reports last week said 45 villages were infested – or whether pre-existing hotspots are only now being
reported.

Worse in store?

Much worse could be in store, however. Hammond noted that many of the Armyworms had now bored into the ground, out of reach of pesticides, and formed protective cocoons around
themselves.

When they re-emerge, after a week to 12 days, it will be as moths. «Each moth can fly up to 1 000 kilometers – and lay 1 000 eggs», Hammond, an entomologist explained.
«Potentially, that’s a recipe for disaster».

One of the possibilities being investigated is to set pheromone traps against male moths. These are baited with the scent females use to lure them into mating – but which would now send
them to their doom.

FAO’s international team includes experts from Ghana, Sierra Leone and Liberia.

Abnormal behaviour

Meanwhile Liberia’s Agriculture Ministry has deployed a set of powerful motorized pesticide sprayers that can reach the Armyworms in the foliage of the tall Dahoma trees where they tend
to congregate. «That’s a very strange way for them to behave», Hammond said. «Normally they like to stay much closer to the ground».

In fact he initially doubted they could be Armyworms, one of the most destructive of insect pests, but positively identified them as such in tests last week.

Hammond could offer no reason for the Armyworms’ abnormal behaviour, which will be verified by experts in the field in about 3-4 days. As to why the insects have reached such large
numbers, he speculated it could be climate-related.

Liberian President Ellen Johnson-Sirleaf, who last month received FAO’s Ceres Medal for Agriculture, declared a state of national emergency on Monday and appealed to the country’s
international partners for help.